For those of you who enjoyed classic shooters, this is a treat. It has retro-borderlands style graphics and the loot mechanics are comparable to that of your basic roguelike game.
Pick your background (prisoner, scientist etc., and there are a LOT!) which essentially defines what you start with in your inventory. You move up randomly generated floors and find loot and kill monsters for exp. When you level, you can unlock a perk (and there are quite a bit to choose from). You can combine materials that you find to create anything from useful items to experimental syringes that yield random buffs/debuffs.
Movement is different than most first person games, whereas you cannot look up or down, but only left and right. You manage your inventory in real time (you'll be doing this quite a bit considering all the items you'll be picking up). You'll also be hacking (mouse cursor dodging mini-game) datapads in real time too so best to clear the floor of enemies before attempting this. You get a random amount of credits (possibly other rewards) for successful hacking attempts.
When you die, you start over, but the 'intel' acquired is persistent. You acquire more and more intel as you replay the game more and more, and with more intel comes more unlockables whether that's more available perks, backgrounds and enemies.
My only gripe is that there are many dead ends, but because you move quite fast (what with the fast paced gameplay), it's negligible.
[Edit] The music also does not loop, so if you're on a floor for some time clearing enemies or hacking datapads, then you'll notice the music will eventually cut out and you'll be left alone in silence.
For the current sale price ($4.99) this game is more than worth it. If you're a fan of roguelike games and enjoyed classic shooters like Duke Nukem and Quake, you'll definitely be getting your money's worth.